Audio amplifier



FIG. 1 is a front view of my new design for an audio amplifier;

FIG. 2 is a rear view thereof;

FIG. 3 is a top plan view thereof;

FIG. 4 is a bottom plan view thereof;

FIG. 5 is a right side view thereof;

FIG. 6 is a left side view thereof; and,

FIG. 7 is a front perspective view thereof.

The ornamental design for an audio amplifier, as shown and described.